Production of netlike structures

ABSTRACT

Thermoplastic net comprising bonded filaments which have at least two different thermoplastic components disposed in generally spirally arranged alternating layers wherein the material of one of the layers is monodirectionally oriented and the remaining material is generally unoriented is disclosed.

United States Patent lnventor Walter J. Schrenk Bay City, Mich. Appl.No. 856,513 Filed July 16, 1969 Division of Ser. No. 505,674, Oct. 29,1965, Pat. No. 3,498,873 Patented Sept. 21,1971 Assignee The DowChemical Company Midland, Mich.

PRODUCTION OF NETLIKE STRUCTURES 7 Claims, 9 Drawing Figs.

US. Cl. 156/167, 18/12,18/13,156/180,156/244,156/441 Int. Cl D04h 3/07,D04h 3/16, B291 3/1 2 Field 01 Search 156/167, 244,441,180; 18/12 N, 12DR, 8 SP, 13 P; 259/3, 9

[56] References Cited UNITED STATES PATENTS 3,014,237 12/1961 Breen18/13 P 3,089,804 5/1963 Gutierrez 156/167 3,118,180 1/1964 Nalle,.lr.18/12N 3,130,959 4/1964 Schrenk et al.. 259/9 3,308,220 3/1967 Smith18/12 N 3,394,433 7/1968 Houvener 18/12 N Primary Examiner-Leland A.Sebastian Assistant Examiner-Roger S. Gaithcr Attorney--Griswold &Burdick ABSTRACT: Thermoplastic net comprising bonded filaments whichhave at least two different thermoplastic components disposed ingenerally spirally arranged alternating layers wherein the material ofone of the layers is monodirectionally oriented and the remainingmaterial is generally unoriented is disclosed.

PATENTEDSEPZI l9?! 3.507.509

sum 2 or 2 NO W M l N VE N TOR. Wa/fer J. Sabre/Ii QMW .QGENT PRODUCTIONOF NETLIKE STRUCTURES This application is a divisional application of mycopending application Ser. No. 505,674, filed Oct. 29, 1965, now US.Pat. No. 3,498,873.

This invention relates to the production of netlike structures and moreparticularly relates to the manufacture of net or netlike fabric fromorganic plastic melts.

A variety of processes are known for the production of netlikestructures by extrusion of an organic plastic melt. Some of suchprocesses which are concerned with the production of a tubular net aredescribed in US. Letters Pat. Nos. 2,919,467; 3,089,804 and the like.Such tubular net is prepared by the extrusion of plastic melt throughrotating extrusion orifices which periodically coincide or by theextrusion of filaments which are combined after emerging from the dieand are still in heatplastified form.

As yet, no ideal singular synthetic organic thermoplastic resinousmaterial has been devised which provides all the desired physicalproperties. ftentimes, it is desired to provide net having an appearancesubstantially significantly different from that which an be obtainedfrom a singular melt and also it is oftentimes desired to provide a netwherein the individual stands have improved physical characteristicsover net obtainable with a single synthetic resinous thermoplasticmaterial.

These benefits and other advantages in accordance with the presentinvention are achieved by providing, as an article of manufacture, asynthetic resinous thermoplastic net comprising a plurality of filamentsbonded together to form such a net, the improvement which comprises eachof the filaments comprising apparently a plurality of layers of diversesynthetic resinous materials, the layers being intertwined.

Such a net is readily prepared in accordance with the method of thepresent invention in an operation for the extrusion of syntheticresinous thermoplastic net by passing an annular heat-plastified streamof synthetic resinous thermoplastic material through a restrainingconfiguration and in contact with at least one rotating surface,extruding the stream through a plurality of apertures rotating relativeto one another and forming a netlike structure, subsequently cooling theextruded stream below the heat plastifying temperature to form asynthetic thermoplastic resinous net, the improvement which comprisesproviding an annular stream which comprises at least two diverse unmixedheat-plastified synthetic resinous components, wherein the resinouscomponents appear to form a plurality of layers.

The method of the invention is particularly adapted to be practicedemploying an apparatus, with comprises in cooperative combination anapparatus for extruding the synthetic resinous thermoplastic netcomprising a means to supply at least first and second heat-plastifiedstreams of synthetic resinous thermoplastic material, a housing, thehousing defining an internal generally cylindrical passageway having afirst end and a second end, the housing defining a first plurality ofpassageways providing communication between the first end of thepassageway and the first polymer supply means and a second plurality ofpassageways providing communication between the second polymer supplysource and the first end of the annular passageway, the first pluralitypassageways communicating with the first polymer source being ingenerally alternating arrangement with the second polymer source, arotor having a first end and a second end, the rotor being rotatablymounted with the housing passageway, the housing and the rotor definingan annular passageway, the first end of the rotor being disposedadjacent the first end of the passageway, the second end of the rotorbeing disposed adjacent the second end of the passageway, the housingdefining a plurality of extrusion apertures adjacent the second end ofthe passageway, the rotor defining a plurality of extrusion orificesadjacent the second end of the rotor and means to rotate the rotarrelative to the housing.

Further features and advantages of the present invention will becomemore apparent from the following specification when taken in connectionwith the drawings wherein:'

'FIG. 1 illustrates an apparatus to be employed in practice of themethod of the present invention.

FIG. 2 is an end view of the terminal portion of the apparatus of FIG.1.

FIGS. 3, 4 and 5 depict alternate feed arrangements which are employedwith the apparatus of FIG. 1.

FIG. 6 depicts an alternate configuration of the terminal end of theapparatus of FIG 1.

FIG. 7 is a schematic representation of a portion of not prepared inaccordance with the method of the invention.

FIGS. 8 and 9 are enlarged schematic cross sections of net filamentsprepared in accordance with the method of the invention.

In FIG. 1, there is illustrated an apparatus to be employed for practiceof the method of the present invention generally designated by thereference numeral 10. The apparatus 10 comprises in cooperativecombination a housing 11. The housing 11 defines an internal generallycylindrical passageway 12 having a first end 13 and a second end 14. Thehousing 11 defines a first polymer passageway or plenum 15 disposedgenerally adjacent the first end 13 of passageway 12. A second polymerpassageway or plenum 17 is generally concentrically disposed about thefirst polymer passageway 15. The passageway 15 is in operativecommunication with a first polymer source 18 by means ofa passageway 19defied by the housing 11. The plenum or distribution chamber 17 is incommunication with a second polymer source 21 by means, of a passageway22 defined by the housing 11. The housing 11 defines an internal annularcavity 23 particularly suited and adapted to receive a heat exchangefluid. The housing 11 generally adjacent the second end 14 defines aplurality of extrusion orifices 25 which are in full communication withthe second end 14 of the passageway 12. A cylindrical sleeve 27 isdisposed within the passageway 12 and is journaled therein by means of abearing 28. A driving means or sprocket 30 is secured to the sleeve 27is adapted to be rotated by means of a power source or drive chain 31.The drive means or sprocket 30 is secured in the passageway 13 by meansof bearing 32 and 33. A distributor ring or feed port block 35 isdisposed adjacent the first end 13 of the passageway 12. The feed portblock 35 defines first and second pluralities of passageways 37 and 38in alternating arrangement. The passageways 37 provide communicationfrom the plenum 15 with the peripheral portion of the passageway 12adjacent the end 13 while the passageways 38 provide communicationbetween the plenum I7 and the first end 13 of the passageway 12 anddischarge thereinto in an alternating fashion. A rotor 40 having a firstend 41 and a second or terminal end 42 is disposed within the passageway12 of the housing 11. The rotor 40 has an outer generally cylindricalsurface 44 which in cooperation with the inner surface of the sleeve 27defines an internal annular extrusion passageway 46 within the housing11, A plurality of extrusion orifices 47 are defined by the second end42 of the rotor 40. The extrusion orifices 47 are disposed in a circularmanner and generally adjacent the orifices 25 adjacent the terminal end42 of the rotor and the terminal end 14 of the passageway 12. Theannular passageway 46 has an outwardly flaring tapered section 48.

In FIG. 2 there is illustrated a view of the second end 42 of the rotor40 and of the passageway 14 of the housing 11 showing the momentaryrelationship between the extrusion orifices 25 and 42.

FIG. 3 is a view of feed port block 35 taken along the line 3- 3illustrating the relationship between the passageways 37 and 38.

In operation of the apparatus as illustrated in FIGS. 1, 2 and 3, afirst thermoplastic resinous material from the source I8 flows throughthe passageway 19 and the plenum 15 through the passageway 37 of thedistributor block 35 and into the annular passageway 46, through thepassageway 46 and is extruded from-the orifices 25 and 46. A secondheat-plastified synthetic resinous material is supplied by the polymersource 21 to, the passageway 22 which in turn passes to the plenum l7and through the passageway 38 of the feed block 35. As the diversepolymers are supplied to alternating passageways, the composite streamformed within the passageway 46 has a longitudinally stripedconfiguration. Rotation of the rotor 40 causes the elements of the firstpolymer and the second polymer to be wound about the rotor in agenerally spiral fashion causing them to be stretched and thinned. Asthe polymer passes from the first end 13 to the second end 14 of thepassageway 12, the speed of rotation relative to the rate of feed isreadily adjusted to provide a heat-plastified stream adjacent the secondend 42 of the rotor having a configuration of a multilayer tube withlaminae spiraling from the inside surface to the outer surface.

Beneficially, rotation of either the rotor 40 or the sleeve 27 causesthe orifices 25 and 46 to periodically coincide resulting in theextrusion of a netlike structure. A netlike structure is obtained whenthe rotor is rotated, the sleeve is rotated or if both the sleeve androtor are rotated at a different rate or if the sleeve and rotor arerotated in opposite directions at a like or different rate. In order toobtain a netlike structure such as is illustrated in FIG. 7, the rate ofrotation of the rotor and the sleeve is the same and the direction ofrotation is opposite. By varying the relative rates of rotation of thesleeve and the rotor, and the feed rate of materials thereto, varyingintertwined spiral patterns are obtained in the cross section of theresultant net.

Employing the feed block of FIG. 3, each filament of the net obtainedhas both of the plastic components generally equally disposed adjacentthe surface thereof. Oftentimes it is desirable to maintain a higherproportion of one polymer adjacent the surface. An arrangement isillustrated in FIG. 4 which depicts a view of an alternate feed blockdesignated 35a having a plurality of passageways 37a and 38a definedtherein. The passageways 38a are adapted to provide communication withthe Plenum 17 whereas the passageways 37a provide communication with thepassageway 15. Thus, the resultant stream within the annular passageway46 without motion of either the rotor 40 or the sleeve 27 results in atubular or annular stream of synthetic resinous thermoplastic materialsupplied from the source 18 having encapsulated therein, streams ofmaterial supplied from the second polymer source 21. On relativerotation of the rotor 40 and the sleeve 27, the portions of the streamof the second polymer, that is, the polymer issuing from the passageways380, are extended to form a plurality of layers encapsulated within acontinuous phase of the first polymer issuing from the passageways 37a.

FIG. 5 depicts an alternate embodiment of a feed block designated as 35bhaving a plurality of passageways 37b and 38c. In a manner similar tothe results achieved in FIG. 4, a plurality of layers of materialissuing from the ports 38c are encapsulated within the material issuingfrom the ports 37b and on relative rotation of the rotor 40 and thesleeve 27, a stream is obtained which has an outer layer of the materialfrom the first polymer source, an inner layer comprising a plurality oflayers of the material from the second polymer source, a layer ofmaterial from the first polymer source 18, a further layer or laminae ofthe material from the second polymer source interspersed with thematerial from the first polymer source and a fifth layer or inner layerof material from the first polymer source. Thus, the material of thefirst polymer source is a matrix containing two layers of spirallyarranged alternating layers of material from the first and secondpolymer sources.

FIG. 6 depicts an alternate configuration of the terminal portion of theapparatus 10 generally designated by the reference numeral 50 showing arotor terminal portion 42a and a housing terminal portion 11a. Thehousing terminal portion 110 has disposed therein a plurality ofpassageways 25a which are in communication with the internal annularpassageway such as the passageway 46. The terminal portion of the rotor42a has a plurality of passageways 46a which are also in communicationwith the internal annular passageway 46. The embodiment of FIG. 6 isparticularly suitable for the preparation of net in accordance with thegeneral procedure set forth in U.S. Letters Pat. No. 3,089,804, whereinthe net is formed externally to the die rather than as it leaves the diein the case of the embodiments of FIGS. I, 2 and 3. The feed block asillustrated in FIG. 5 is particularly advantageous and beneficial whenemployed with the modification illustrated in FIG. 6 as the streams ofthe polymer emerging from the orifices 25a and 46a comprises materialfrom the ports 37b, that is, the first polymer source, is disposed inhigher proportion at the surface of the filament and partiallyencapsulates a number of intertwined layers of material from the firstand second polymer sources, and in cases where the polymers from thefirst and second sources do not readily adhere to each other, a bond isobtained between the filaments of the net as the outer portion of eachof the filaments contains a predominant amount of material from thefirst polymer source.

In FIG. 7 there is schematically illustrated a portion of net generallydesignated by the reference numeral 55 prepared by either theembodiments FIGS. 1, 2 and 3, or the modification of FIG. 6 whenrotation of the rotor and sleeve is maintained at an equal rate but inopposite directions.

In FIG. 8 there is illustrated a schematic enlarged sectional view ofthe terminal portion of a filament of a net such as the net 55 generallydesignated by the reference numeral 60. The filament 60 is composed of aplurality of layers a and b which are intertwined and each of the layersa andb terminate generally adjacent the outer surface of the filament.

In FIG. 9 there is illustrated a cross-sectional configuration of bondedfilaments generally designated by the reference numeral 65. Thefilaments 65 are prepared employing the apparatus 10 with the exceptionthat the feed block 35 has been replaced with the feed block 35a. Thefilament 65 comprises an outer layer of material designated as a fromthe first polymer source and an inner region of alternating spirallydisposed layers of material a and material I). The filaments, inaccordance with FIG. 9 are also prepared when the apparatus OF FIG. 1 ismodified to incorporate the feed block arrangement 35b in conjunctionwith the arrangement of extrusion orifice illustrated in FIG. 6.

By way of further illustration, a plurality of nets are prepared havinga configuration generally as illustrated in FIG. 7. The followingcombinations are found to give highstrength nets resistant tofibrillation; high-density polyethylene and low-density polyethylene;Nylon 66 and polyethylene; Nylon 66 polyvinylchloride; Nylon 66 and ablend of parts of polystyrene and 20 parts of butadiene rubber; Nylon 6and a copolymer of parts vinyl chloride and 15 parts vinyl acetate;polypropylene and polyethylene; polypropylene and a copolymer of 80parts polyvinyl chloride and 20 parts butyl acrylate; polypropylene anda blend of 80 parts of polystyrene and 20 parts by weight of butadienerubber; polystyrene and polyethylene; a copolymer of parts by weightvinylidene chloride and 10 parts by weight vinyl chloride andpolyethylene; and a copolymer of 90 parts by weight vinylidene chlorideand 10 parts by weight vinyl chloride and a copolymer of 85 parts ofvinyl chloride and 15 parts of vinylidene chloride. In each case, thetemperature of the extruded stream was maintained at the optimumtemperature for the orientation of orientable phase. obtained and theyexhibit great resistance to fibrillation. The resultant products onsectioning, had a configuration generally resembling that of FIG. 8,wherein intertwined layers of the two polymers are attained in theindividual filaments of the net. The product beneficially may be heattreated and stretched in the conventional manner to attain desirablephysical properties arising from orientation at suitable temperatures.

In order to attain a net having a maximum service life, it is desirableto employ as one component, an orientable material which is relativelyrigid and a softer material such as high pressure polyethylene or aplasticized polyvinyl chloride. By treating the extruded net, in amanner which favors maximum physical properties, by monodirectionalorientation of the orientable component, generally the net exhibits thehigh tensile strength of the orientable component and elongation of thesofter or less rigid component. It is not necessary that the polymersadhere to each other strongly, as the extrusion is accomplished in theabsence of an atmosphere and beneficially the layers within the polymerhave a thickness of from about 0.001 mil, and beneficially 0.2 mil.

Beneficially extruded net in accordance with the present invention isreadily produced employing wide variety of oriented polymers. Typicaloriented polymers or components which are utilized in the production oftwo component nets in accordance with the present invention includepolypropylene, polystyrene, styrene; including Nylon 66 the condensedproducts of hexamethylene diamene and adipic acid, Nylon 77,polycaprolactan or Nylon 6, crystalline vinylidene chloride polymerssuch as a copolymer of 85 weight percent of vinylidene chloride and 16weight percent of vinyl chloride; linear polyesters such as polyethyleneterephthlate, rubber hydrochloride, copolymers of styrene adacrylonitrile such as a copolymer containing 72 weight percent styreneand 28 weight percent acrylic acid, rigid polyvinyl chloride, polymethylmethacrylate, polycarbonates, irradiated polyethylene, polyvinylfluoride and the like.

Beneficial for the nonoriented, poorly oriented or synthetic orientedcomponents, advantageously there is employed plasticized polyvinylchloride, polyethylene, rubbers of both the natural and syntheticvariety, copolymers of ethylene and propylene, copolymers of ethyleneand ethyl acrylate and like materials.

The thickness of the layers, in the net filaments, is readily controlledby the relative rate of rotation, of the mandrel or rotor, and the outerhousing and the rate of throughput of the molten polymer. Thus, if therotational rate is excessive relative to the throughput rate, a productis obtained which is apparently a single phase material when the layersbecome vanishingly thin. As the relative rate of rotation is reducedwith constant throughput, the layer thickness is increased.

Employing the modification of FIG. 6, and the feed block of FIG. 4, inthe apparatus of FlG. l, polyethylene is fed from the feed ports 37a andthe polystyrene feed ports 38a, the proportion of polyethylene topolystyrene is about 1 to 1.5. The resultant net filaments have aconfiguration such as is generally illustrated in FIG. 9. Excellentadhesion is obtained at the junctions between the filaments and theresulting net exhibits a high tensile strength and elongation.

By utilizing polymers of diverse color and/or refractive index, nethaving unique appearance is obtained.

As is apparent from the foregoing specification, the present inventionis susceptible of being embodied with various alterations andmodifications which may differ particularly from those that have beendescribed in the preceding specification and description. For thisreason, it is to be fully understood that all of the foregoing isintended to be merely illustrative and is not to be construed orinterpreted as being restrictive or otherwise limiting of the presentinvention, excepting as it is set forth and defined in the heretoappended claims.

1. A method for the extrusion of a synthetic resinous thermoplastic netcomprising, passing a single heat-plasticized stream of syntheticresinous thermoplastic material through an annular elongated restrainingconfiguration with the annular steam being in contact with at least onerotating surface, extruding the stream through a plurality of concentricapertures to form a plurality of filaments, rotating the apertures andthe filaments relative to one another to form an annular netlikestructure, subsequently cooling the extruded netlike structure below thehcat-plasticizing temperature, wherein the improvement comprisesproviding two diverse unmixed heatplasticized resinous components toform the annular stream forming the stream initially with at least oneof the components extending from an inner surface of the stream to anouter surface of the stream, rotating the inner surface of the streamrelative to the outer surface of the stream, forming by the rotation ofthe stream an apparent plurality of layers generally spirally dis osedwithin that stream.

2. The method 0 claim 1, wherein the net lS subsequently stretched at atemperature suitable for the orientation of at least one of thethermoplastic resinous components.

3. The method of claim 1, wherein the annular stream has an outer layerof one of the resinous components.

4. The method of claim 1, wherein the stream is extruded as a pluralityof filaments which are contacted in the heat plastified form outside ofthe extrusion apparatus.

5. The method of claim 1, wherein the layers in the annular stream havea generally spiral configuration, when the stream is viewed in axialcross section.

6. The method of claim l, wherein annular stream is disposed betweengenerally cylindrical confining walls which rotate relative to oneanother.

7. The method of claim 6, wherein the walls are counterrotating.

" UNITED STATES PATENT OFFICE "a s9 7* mm esnrnieirs er eoesrt'menPatent No. 3,6OT,509 Dated 21 September 1971 Inventor(s) Walter J.Schrenk It is certified that error appears in the above-identifiedpatent and that said Letters Patent are hereby corrected as shown below:

In column 1, line 21, delete "an" and insert can in line 23 delete"stands" and insert strands In column 2, line 26 delete "defied andinsert defined in line 37 delete "TO" and insert and In column 4, lineif! insert and between 66" and "polyvinylchlorideg" in line 62 insertNets of high tensile strength are between "phase." and "obtained" Incolumn 5, line 19, delete "ad".,and insert and In column 6, line 16,delete "steam" and insert stream in line 28 delete "rotation" and insertrotating Signed and sealed this 23rd day of May 1972.

EDWARD ihFLiiiTCIiER ,JR. ROBERT GOTTSCHALK ttostin fficer Commissionerof Patents

2. The method of claim 1, wherein the net is subsequently stretched at a temperature suitable for the orientation of at least one of the thermoplastic resinous components.
 3. The method of claim 1, wherein the annular stream has an outer layer of one of the resinous components.
 4. The method of claim 1, wherein the stream is extruded as a plurality of filaments which are contacted in the heat plastified form outside of the extrusion apparatus.
 5. The method of claim 1, wherein the layers in the annular stream have a generally spiral configuration, when the stream is viewed in axial cross section.
 6. The method of claim 1, wherein annular stream is disposed between generally cylindrical confining walls which rotate relative to one another.
 7. The method of claim 6, wherein the walls are counterrotating. 